Exemplary embodiments of the present invention relate to a semiconductor memory designing technology, and more particularly, to a fuse circuit including a programmable fuse and a method for operating the same.
In general, a semiconductor memory device is integrated with a lot of memory cells. If any one of the memory cells has a failure, the semiconductor memory device including the memory cell with a failure is recognized as a defective product and abandoned. Since the number of memory cells integrated in a semiconductor memory device is increasing more and more, it is not economical to abandon a semiconductor memory device just because one memory cell has a failure.
To resolve this problem, semiconductor memory devices include a fuse circuit along with a redundancy memory cell. The fuse circuit is programmed with the address of a memory cell having a failure, and is used to determine whether or not to access a redundancy memory cell. Herein, the term “program” means a series of operations of cutting or not cutting a fuse included in the fuse circuit for a corresponding target data. Generally, a fuse is cut using laser beam.
Meanwhile, a cut fuse may subsequently undergo an electrical and chemical migration. As a result of this phenomenon the fuse may become reconnected. A reconnected fuse is an undesirable defect and may cause a failure in the semiconductor device. Such a failure frequently occurs when copper is used as a material for metal wiring, but it may occur when aluminum or other materials are used. Also, such a phenomenon may occur during a test operation performed at a high temperature and high voltage. Subsequently, since the failure may occur after a packaging process, it is difficult to detect the failure and even if such a failure is found out, it is hard to correct the circuit. Therefore, such a failure becomes a factor of deteriorated productivity, performance and reliability of semiconductor memory devices.